We propose to evaluate the 1-year efficacy of an after school team sports program for reducing weight gain among low-income children whom are at-risk of overweight and overweight. We hypothesize that at-risk and overweight children who have an opportunity to participate in team sports with other at-risk and overweight children will be more likely to participate in regular physical activity and make it a part of their routine, resulting in decreases in body mass index (BMI) and increases in total daily physical activity and self-esteem. Initial data from our ongoing feasibility study suggest that at-risk and overweight children will join, attend, and enjoy being a part of an after school team sports program. We propose a 12-month randomized controlled pilot trial (RCT) comparing BMI changes among at-risk and overweight children randomized to participate in the after school team sports program or a traditional nutrition education program. The RCT will enroll a total of 90 4th and 5th grade children from the Ravenswood School District in East Palo Alto, a low-income, primarily Latino, African American and Pacific Islander community. The primary outcome is BMI. Secondary outcome measures include waist circumference, triceps skinfold thickness, physical activity monitoring (with accelerometers) and selfesteem. We will also collect process data to examine the implementation of the program and potential mediators of intervention response. We will compare the intervention and control groups using random regression models. If our proposed research finds that team sports are an efficacious intervention for reducing weight gain among low-income, at-risk and overweight children, it is an intervention approach that could be rapidly diffused and tested for effectiveness. In addition, our study will generate valuable knowledge on potential physical, psychological, social and process factors that may moderate or mediate successful intervention effects to help inform future research into the prevention and treatment of obesity. [unreadable] [unreadable]